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If a photon passes through a region of space, will that region of space exert a gravitational pull on a particle outside it? (lemm.ee)

submitted 1 year ago* (last edited 1 year ago) by Hedup@lemm.ee to c/askphysics@lemmy.world

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Also, would a region of space where light spends more time traversing it become more massive than a similar region of space where light doesn't spend that much time all else being equal?

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[–] OccamsTeapot@lemmy.world 1 points 1 year ago

Not 100% certain but I think the answer is yes. In general relativity the main equations revolve around two things: the metric tensor and the stress energy tensor. And of course we all know that a tensor is the thing that acts like a tensor (j/k but I probably can't explain properly, lol).

The metric tensor is (basically) describing the gravitational potential across spacetime, so the mechanism of 'pulling' a particle. And the stress energy tensor has the information about the energy and momentum flux in the region, which is what affects the structure of spacetime (ie the metric). So mass creates this flux and we get normal everyday boring gravity and also photons create an energy flux, and make some kind of funky but functionally identical but very weak gravity.

It wouldn't really be noticeable in practice. I would be interested to see the maths done but don't want to spend Sunday working out tensor components.

For the second part I don't know, in a way? If a region has more stars moving through it, leaving and then some time after another one coming, does that region have more gravity? In a way I guess